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  • maxprime@lemmy.mltoWikipedia@lemmy.worldUnknot
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    2 months ago

    Similar, but not the same.

    A knot is an embedding of a circle. So one takes a circle, and twists it up in whatever fashion they desire. Slightly more formally, It’s a continuous collection of points in 3D that does not overlap and begins where it ends.

    The unknot is just a knot that is topologically equivalent to a circle. Like an elastic band. At rest, it can look just like a circle. But you can twist it up whichever way you like. It won’t look like a circle but you know that you can undo all of the twists and get back to the original shape.

    It’s sometimes easier to think of a knot that is not the unknot: like the trefoil knot. No matter how much you fiddle with it it’s not going to be an unknot.


  • Here is an AI generated summary.

    1. The host, C, tests various USB-C cables, including an original MacBook cable, a certified 240W Apple cable, and a Thunderbolt 4 cable.

    2. The original MacBook cable can handle up to 100W and operates at USB 2.0 speeds (480 Mbps).

    3. The original cable is identified as an active USB PD cable, capable of 20V and 5A, but lacks support for USB 3 or 4.

    4. The 240W rated cable also operates at USB 2.0 speeds and can handle up to 48V and 5A, indicating suitability for higher power delivery.

    5. Both cables are confirmed to be genuine Apple products with similar vendor IDs, and their condition is noted to be in good health.

    6. Limitations of the tested cables regarding data transfer capabilities are highlighted, while their charging potential is emphasized.

    7. The speaker discusses testing various Thunderbolt cables, confirming compatibility and correct functionality.

    8. Performance metrics for the Thunderbolt cables include a data speed of 40 Gbps and a charging power of 100 watts, with a warning about a “shorted pin.”

    9. The cables claim to support USB 4 capabilities, with technical details provided about voltage and amperage ratings.

    10. All tested cables are operational for charging a MacBook, though a more powerful charger and cable may be necessary for higher power demands.